Engine Sensors - Part 1 Oxygen Sensors

[SIF]

unplugging the 02 sensors will give you worse gas mileage. 02 sensors are there to optomize fuel economy.

-Drew

A huge increase? Sorry just done a search and a previous thread implies 'better than a carb fed engine'.

 

[Peter Westling]

Some more info..

I stumbled across some nice info about our belowed O2 sensors.
I thought I should contribute with it:


Sensor Testing:
The Lambda Sensor is at the heart of emission control continually monitoring the exhaust gas. Carbon Monoxide (CO) is produced by the engine. If the mixture supplied is too rich then CO will be high and visa versa. Having plenty of fuel (Rich) the engine will try to burn as much as possible, using up all available Oxygen, conversely if there is not sufficient fuel to maintain a correct burn then the excess Oxygen will pass into the exhaust system.

Rich mixture = High CO = Low Oxygen
Weak mixture = Low CO = High Oxygen

The Zirconia lambda sensor, by using precious metals, can determine the Oxygen difference between atmosphere and the exhaust gasses. The greater this difference, the higher the voltage it will produce, up to app 1volt. Lambda sensors will not operate until around 300 deg. They are heated by the exhaust and often have their own heater element. Single & twin wire lambda sensors have no heater element and are usually situated near or in the manifold, three & four wire sensors have an built in heater to aid rapid warmup and may be placed further downstream.

From the table it can be seen that the voltage produced changes significantly within the window lambda 0.97 - 1.03. The ECU monitors this voltage and can correct the mixture strength (by changing the injector open time) to try to maintain perfect combustion.

The sensor can be tested for output by connecting to it a digital voltmeter, set to a 2v scale. Connect the +ve test lead to the sensor signal wire and the -ve test lead to earth/battery -ve. The voltage produced should swing from app 0.2v to 0.8v and back around once per second. If the voltage is stuck high then the engine is probably running rich for some other reason. If stuck low then usually either a faulty Lambda Sensor, air leak or an engine running very weak for some reason.

The newer type of lambda sensor (titania) work on a different principle, changing a supplied voltage as against creating one, but they still measures the Oxygen differences. These later types are generally more accurate and responsive.


Common Sensor Faults:

A: Antifreeze Contamination

Antifreeze in the exhaust will attack and destroy the sensing element. A leaking head gasket commonly causes antifreeze contamination.

B: Rich Fuel Mixture

This will cause a heavy black carbon layer to form on the sensor element. Rich fuel mixture is usually caused by a failure in the air/fuel metering system

C: High Oil Consumption

This will coat the sensing element with a crusty, brown layer. Worn piston rings and valve guides, or other internal engine problems can cause high oil consumption.

D: Silicone Poisoning

Residue from silicone lubricants will rapidly destroy the sensor’s element. Care should be exercised not to get silicone lubricants on the oxygen sensor when it is being installed.

Common Sensor Variations.


To be sure of fitting the correct replacement oxygen sensor it is good to have an understanding of the different types. The most common is the zirconia dioxide (Zirconia) sensor, which comes in heated and unheated form. There are two different types of zirconia sensor and some manufacturers use titanium dioxide (titania) oxygen sensors. Below is a general overview of each type of oxygen sensor:

Zirconia 'thimble' type
Element type - zirconium dioxide, thimble
Types available - one, two, three and four wire, 18mm thread
Heater resistance - (3 and 4 wire sensors only) 2 to 6.5 ohms
Output signal - oscillating 0.1 and 0.9 volts


Zirconia ‘thick film’ type
Element type - zirconium dioxide, planar
Types available – four wire, 18mm thread
Heater resistance - 12 to 15 ohms
Output signal - oscillating between 0.1 and 0.9 volts


Titania
Element type - titanium dioxide, planar
Types available - three and four wire 12mm and 18mm thread
Heater resistance - 4 to 7 ohms.
Output signal - oscillating between 0 and 1 volt or between 0 and 5 volts
(depending on make and number of wires)


Lean Burn
Element type - zirconium dioxide, thimble or planar
Types available - four wire, 18mm thread
Heater resistance - 12 to 15 ohms
Output signal - discrete voltage levels between 0 and 5 volts



Function:
The Oxygen Sensor (also known as Lambda Sensor) is located in the exhaust manifold and measures the amount of unburned oxygen in your engine's exhaust. Based on the amount of oxygen, it sends a signal to your engine computer which then adjusts the air/fuel mixture for optimum engine performance and emission control.


Failure Symptoms:
Excessive fuel consumption, a faulty oxygen sensor can waste 30% of your fuel.
Driveability problems, such as engine surging or hesitation.
High hydrocarbon emissions, failing an emissions inspection.
The engine warning light may be on or service flag displayed.
The ecu/computer stores a mixture-related fault code.
When the oxygen sensor has stopped functioning completely, the catalytic converter may overheat and fail


Maintenance/Service:
Test and/or replace every 30,0000 miles.
Perform periodic emission checks.
Watch for service light.
Vehicle manufacturers recommend periodic inspection and replacement of oxygen sensor.


Quick Check List
1. Count the number of wires on the original sensor.
2. Check the colour of the wires
a. If the sensor has black, grey, purple or white wires, it will be a Zirconia sensor.
b. If the sensor has one red wire with the possible exception of some Japanese vehicles, it will be a Titania sensor.
3. If it is a Titania sensor then check the original thread size of the sensor.

* In some applications fitted with three wire Titania oxygen sensors, the output is 0 to 5 volts.

 

[ExplorerDMB]

Here is a thread about what 02 sensors should look like graphed:

http://www.explorerforum.com/forums/showthread.php?t=155495

tease photo:

-Drew

 

[Opera House]

P0153 again! Check engine light on again so I went to AutoZone. They told me O2 sensor after the cat. I'm first to admit that my memory is shot, but after the cat didn't seem right for P0153. Hey, they try! Thought I only replaced that sensor only about a year ago. Checked for my old post. It was 8-5-2003 and about 50K ago. Told you my memory is shot. All my sensors are still factory at almost 200K except Bank 2 Sensor 1. This sensor is killed by a small antifreeze leak that also kills the spark plug about every 10K. Sensor has a green crystal coating that actually blocked the vents. Not wanting to spend good money after bad, I dug into the junk box and found an old sensor from my 92. I had kept that sensor from when when I was trying to solve a lean problem actually caused by an intermitant fuel regulator. Took my grinder and removed the keying tabs on the connector to make it a "universal" sensor. After five days it is still working.

 

[Glacier991]

Terrific input guys, and Thanks OperaHouse.... your frugality is legend and you always have something to teach us all. I too have an original O2 sensor with in excess of 200K on it.... and it graphs out beautifully. Properly cared for (eg. no bad things happening to them, use good gas and no silicone contamination) they CAN last longer than many think.

 

[spindlecone]

Terrific input guys, and Thanks OperaHouse.... your frugality is legend and you always have something to teach us all. I too have an original O2 sensor with in excess of 200K on it.... and it graphs out beautifully. Properly cared for (eg. no bad things happening to them, use good gas and no silicone contamination) they CAN last longer than many think.

Silicone contamination? Glacier Can you elaborate

 

[BrooklynBay]

If you look at some packages of silicone that are used on head gaskets, exhaust gaskets, and other parts, you will see that some of them say that they are good for fuel injected vehicles with O2 sensors, while other ones say that they shouldn't be used. Some of them will ruin an O2 sensor, so always read the warning labels.

 

[Glacier991]

Simply put... any sinicone that comes into contact with an 02 sensor will ruin it.

Silicone has many sources. Including silicone sealants on intake gaskets for example. Look for "Sensor safe" products if you are using them near intakes.

 

[spindlecone]

Simply put... any sinicone that comes into contact with an 02 sensor will ruin it.

Silicone has many sources. Including silicone sealants on intake gaskets for example. Look for "Sensor safe" products if you are using them near intakes.

Thx for the info

 

[BrooklynBay]

These links have information on O2 sensors: http://www.kemparts.com/techtalk/tt07.asp
http://www.gendan.co.uk/article_11.html

 

[moonshadow60]

I recently had a diagnostic run on my 96 explorer v6 4.0. It showed bank 2 sensor 1 out of range and catalytic converter inefficiency. It was suggested that the catalytic converter code may have been triggered by the defective sensor, and that I first replace the sensor. This sounds good to me, as it is less expensive, but from reading the early post on this thread it seems that perhaps an inefficient catalytic converter would cause the o2 sensor to be out of range, not the other way around....... any thoughts or explanations that could elucidate? what are the odds that it is simply an upstream sensor gone bad? thanks!:scratch:

 

[btexpress]

I recently had a diagnostic run on my 96 explorer v6 4.0. It showed bank 2 sensor 1 out of range and catalytic converter inefficiency. It was suggested that the catalytic converter code may have been triggered by the defective sensor, and that I first replace the sensor. This sounds good to me, as it is less expensive, but from reading the early post on this thread it seems that perhaps an inefficient catalytic converter would cause the o2 sensor to be out of range, not the other way around....... any thoughts or explanations that could elucidate? what are the odds that it is simply an upstream sensor gone bad? thanks!:scratch:

Upstream sensor will not set a cat efficiency code. Typically if the cat efficiency code is set, the cat is weak. Is yours a P0420? If so this indicates the sensor is working correctly but the cat is not. Typically on this vehicle if you have a code for one upstream sensor, it is a good possibility the sensor is weak or "lazy".

Upstream sensors are considered oxygen sensors, downstream are catalyst efficiency monitors, technically very similar but different functions.

 

[moonshadow60]

indeed, the code is po420 , and po153 is also reported.
sounds like I need a cat, and maybe a sensor also? thanks.

 

[moonshadow60]

so now I've gone to the catalytic converter thread and it seems to indicate that there is more than one. btexpress: do you know which one the po420 code would be referring to?

 

[btexpress]

P0420=bank 1

 

[axlegrease]

Hi Folks,

To add maybe a little bit of useful information about the switching characteristics of oxygen sensors, the next three images are some homemade oscilloscope screens of my 1992 Ranger (OBD 1) oxygen sensors taken when trying to figure out if they were working ok or not.

BOB 43 & 46 and BOB 44 and 46 are the breakout box connections. The 0.5 V is the vertical scale of 0.5 volts per division and the 0.5s is the horziontal scale of 0.5 seconds per division. The switching is occuring about every tenth engine revolution. Don' pay any attention to the vertical scale readings as there is a scale factor involved.

The time scale has been changed to 0.1 seconds per division. The wiggles across the top and bottom are just ac noise pickup.

Any comments about the switching characteristics would be appreciated.

These were fairly new sensors when the images were made, replacing a pair that were no good.

 

[4x4man]

Some good info here:

http://en.wikipedia.org/wiki/Oxygen_sensor

and here

http://www.asashop.org/autoinc/dec2002/mech.cfm

Thanks...very useful info

 

[034L]

120+ dollars of regret

First time posting, with 120.00 worth of regrets. the scanner is reading bank 1 and bank 2 are running lean, replaced the lower two O2 sensors, still throwing a code, looking for vacuum lines and can only find two, they both look fine, but I can't find where they are going to on the engine, only the little round thing under the air intake on an 03, 4.0 ranger. any suggestions

 

[034L]

I also at times have an extremely rough idle and occasionally have to nurse the throttle to keep it running, however soon as I start driving, it seems to burn off the excess fuel and run fine.

 

[walterGT67]

Thanks for the post..